The British RailClass 73 is a British electro-diesel locomotive. The type is unusual in that it can operate from the Southern Region's 650/750 V DC third-rail or an on-board diesel engine to allow it to operate on non-electrified routes. This makes it very versatile, although the diesel engine produces less power than is available from the third-rail supply so the locomotives are rarely operated outside of the former Southern Region of British Rail. Following the withdrawal and scrapping of the more powerful Class 74 electro-diesels in 1977, the Class 73 was unique on the British railway network until the introduction of the Class 88 electro-diesels in 2017. Ten locomotives have been scrapped.

The Southern Railway expanding third rail electric passenger network (which had begun as far back as 1909) was until 1941 a purely passenger electric multiple unit (EMU) system. However the arrival of electric locomotives designed by Oliver Bulleid (Chielf Mechanical Engineer) and Alfred Raworth (Chief Electrical Engineer) presented a problem with regard to freight operation. It was realised that laying 750 V DC third rail in freight yards would present a serious hazard to personnel on the ground. So the initial solution was to fit a simple tram-like overhead 750 V wire strung from masts, only in selected goods yards, and add a pantograph to the three initial electric locomotives, so they could collect current from the overhead wire, which removed the hazard.

British Railways then began electrifying the main lines to the Kent Coast as part of the 1955 Modernisation Plan. In addition to the few hundred new EMU's required, a small fleet of 25 Bo-Bo electric locomotives of 2,552hp classed type "HA" (later class 71) were built to deal with freight, parcels, and the few remaining locomotive hauled passenger trains in Kent, such as the "Night Ferry" and "Golden Arrow" services. These locomotives also had pantographs, and so a number of more important freight yards across Kent were fitted with the simple 750 V overhead wire system. This system was brought into use across Kent between 1959-61.

Although successful this system did require considerable extra cost, and maintenance, and still limited freight operations with the new locomotives to only those goods yards fitted with the catenary. So something more versatile was needed. Development and advances in both Electric locomotive and Diesel engine design in the early 1960s. Resulted in the Southern Region engineers beginning to consider the possibility of a combined Electric and Diesel locomotive. The requirement was for an Electric locomotive with a similar power on electric to the already successful Type 3 Crompton Diesel locomotives (later Class 33) then entering service on the Southern. This would be supported by adding a small diesel engine powerful enough to move reasonable freight loads at slow speed within goods yards. The new locomotive design would also need retractable 3rd rail pick up shoes. This was primarily to allow these locos to also be used in connection with track relaying jobs. So avoiding the problem of bridging a gap and energising a dead section of third rail, and electrocuting track workers in who might be in contact with the dead third rail section.

The Southern Region engineers having done all the initial design work set about building the first "Prototype" batch of six new "Electro-Diesel" locomotives at Eastleigh Works during 1961-2. The new locomotives were given 1,600 hp on electric and 600 hp from the small Diesel engine. The success of these "Prototype" locomotives, resulted in British Railways ordering from English Electric at the Vulcan Foundry in Newton-le-Willows a production batch of a further 43 locomotives. However minor technical differences prevented the "Prototypes" (Classified type "JA") working in multiple with the production examples (Classified type "JB"). In all other respects the new "Electro-Diesels" proved extremely versatile, to the point where many are still in service after a life of over 50 years.

On 26 April 1968, locomotive E6023 was derailed at Earley, Berkshire when a set of points were moved by mistake.[1]

On 8 January 1972, locomotive E6027 collided with 4-BEP no 7004 at Horsham, injuring 15.[2]

On 12 October 1972, locomotive E6001 was hauling a freight train that ran into the rear of a passenger train at Wimbledon, London due to inattentiveness on the part of the driver. Twelve people were injured.[3][4]

On 16 January 1982, 73 115 was hauling a departmental train which overran signals and ran into the rear of a parcels train at East Croydon.[5] The severely damaged locomotive was withdrawn and subsequently scrapped.[6] Locomotive 73 006 was hauling the parcels train that was run into.[5]

This class of 49 locomotives were built in two batches using English Electric components. The first six locomotives were built by BR at Eastleigh works in 1962 and were numbered E6001-E6006 and classified as type JA.[7] With the introduction of TOPS in 1968 they were to have been classified as Class 72, to differentiate from the later built units. However, instead they became Class 73/0. In the early 1970s the locomotives were renumbered 73001-73006.

Following successful trials of the initial locomotives, a production run of 43 locomotives were built by English Electric at their Vulcan Foundry between 1965 and 1967. They were initially classified as Class JB and numbered E6007-E6049.[7] They differed slightly from the six earlier machines, most notably having an increased tractive effort as well as a higher maximum speed (90 mph as opposed to 80). Following the introduction of TOPS, they became Class 73/1 and were renumbered 73101-73142. One locomotive, E6027, had already been withdrawn following accident damage and so was not renumbered. Further changes were the use of large round Oleo buffers with a pneumatic withdrawal mechanism rather that the traditional coach style (oval) saddle buffer which relied on a pin and spring mechanism. As the JA examples came in for overhaul over the years, the saddle buffers were also replaced making visual identification of the differing machines almost impossible from a distance.

These locomotives were equipped to operate from the 650 or 750 V DC third-rail or an on-board diesel engine to allow it to operate over non-electrified routes.

Electrical power was gathered in the normal manner of collector shoes which ran along the top of the third rail. There are two shoes mounted on either side of each bogie which could be retracted when not in use to avoid damage as they were prone to drop out of gauge slightly when not under pressure.

A major design flaw with the class was that the traction current circuits of each bogie were not isolated. The third rail supply is generated close to the rail line and there are many areas where it changes from one substation to another. Although great effort is made to ensure the voltages are the same between sections, at the extreme ends of supply there can be very large differences due mainly to voltage drops caused by other electric trains. There are examples of fires in class 73 where the locomotive has acted as an electrical bridge between two different substations causing the traction circuit inside the locomotive to take the brunt of the huge surges in supply as trains move in and out of the sections behind and in front. This problem was particularly noticeable at junctions where conductor rails cannot be separated by a good distance and many of the class were damaged by fire caused in this manner over the years. Class 73s were well known for incredible displays of arcing at the collector shoes for this exact reason.

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Unlike the previous Southern Region Class 70 and Class 71 electric locomotives, these did not have a booster to maintain traction power over gaps in the conductor rail. However, they could move forward onto an electrified section under diesel power.

The 600 horsepower (447 kW) English Electric 4SRKT Mk II diesel engine was less powerful, but more reliable than the 650 horsepower (485 kW) Paxman 6YJXL fitted to the later
Class 74 electro-diesel locomotives.

Multiple working was to the standard SR 27-wire system a design that ensured excellent compatibility. They could work with other 33/1, 71, 74, most Southern Region electric multiple units and diesel electric multiple units built 1956-74. Having electro-pneumatic control, class 73 multiple working was also possible with Blue Star coupling-coded mainline diesel locomotives of types 2, 3 and 4 - though such operational combinations were rare. Delivery of class 73/1 from Vulcan Works was with the locomotives under power, most often as light-engine moves. Many such movements also included deliveries of later-build class 20 (blue-star coded) in tow. Both locomotives would be under power with a single crew and the trip south would constitute part of the "burn-in" of both diesel engines. On such moves, the class 73 would often work into Doncaster yard, drop off the '20 and continue south to Stewarts Lane depot in South London all in a single move. As an aside here, such was the reliability of both the design and build, the '73 would often be put to work the same day of arrival after examination by the reception fitters.

Incompatible coupling codes required two locomotive crews. Waterloo - Exeter services traditionally used locomotives borrowed from the Western Region and this service was a mainstay for "Warship" class 42/43 locomotives. Over the years, this class suffered badly from vacuum train brake failures and the Stewarts Lane standby was often called to assist. 73+42 combinations have been noted leading Exeter trains as far as Basingstoke or Salisbury where the failed locomotive would be replaced. Ironically, the class 73 on electrical power was capable partner for the Warship and any delay in the service leaving was usually made-up by the time the train arrived at Basingstoke.

73966, Class 73 Electro-diesel in Caledonian Sleeper livery at Fort William Station

During 1984, a small subfleet of Class 73s were dedicated to work the upgraded Gatwick Express service, which would feature a Class 73 at the southern end, a rake of air-conditioned Mk2f coaches which had been modified to carry Southern Region multiple unit control jumpers, and a Class 489 "GLV" (themselves converted from former Class 414 driving Motor coaches) at the north end. Both the Class 73 and the GLV provided power, and the trains ran non-stop between London Victoria and Gatwick Airport.

Since privatisation, the Class 73 fleet has been reduced in size following the large-scale withdrawals of the EWS and Gatwick Express fleets. However, many smaller operators have acquired locomotives, so their continued use is assured for the foreseeable future.

Eurostar owns and formerly operated two Class 73 locomotives, which were specially modified to enable them to haul a Eurostar unit. The two locomotives; 73118 and 73130, have additional coupling equipment fitted and were primarily used to rescue failed Eurostar sets, or to haul them over non-electrified routes. They were rarely used away from North Pole depot. When Eurostar moved its operations to the new Temple Mills depot and onto the overhead wiring of High Speed 1 in 2007, the Class 73 locomotives became redundant and were loaned to educational initiatives: 73130 went to RailSchool in East London and 73118 went to Barry Rail Centre in South Wales. Subsequently, when RailSchool failed, 73130 was loaned to the Bluebell Railway but is stored away from the railway.

FM Rail (previously Fragonset Railways) bought several redundant locomotives from EWS. Most of these were initially stored at various locations around the country, including preservation sites, such as the Mid-Hants Railway, the Peak Railway and the Dartmoor Railway. Some of these locomotives were repaired for use on these heritage railways, such as number 73134 on the Dartmoor Railway.

One locomotive, number 73107 "Spitfire" returned to mainline traffic in 2004 following overhaul. It was repainted in Fragonset's black freight livery, and was expected to be used on empty coaching stock moves associated with charter trains. It was regularly hired to First GBRf from late 2004 as cover for their fleet and was based at c2c's East Ham Depot along with the Blue Pullman Rake. In 2007 it was acquired by RT Rail and has been overhauled and repainted in a GBRf-esque livery at St. Leonards Depot.

Until mid-2005, Gatwick Express operated several Class 73s with Mk 2 EMU sets with GLV luggage vans.
These have now been withdrawn and replaced by EMUs. However, 73202 was retained as a "Thunderbird" engine to rescue failed EMUs. Along with the rest of the Gatwick Express franchise, it later passed to Southern. The locomotive, formerly "Dave Berry", was renamed "Graham Stenning" after the company's Apprentice Manager, at Brighton Lovers Walk Depot on 11 December 2015.

GB Railfreight is the newest operator of Class 73 locomotives, having bought six redundant Gatwick Express locomotives, numbers 73203-207 and 73209. Four of these (73204-206 and 209) have now been returned to traffic after overhaul by Fragonset at Derby. They have been repainted in the company's blue and orange livery, and named after female employees. The locomotives are primarily used on engineering trains originating from Eastleigh and Tonbridge. The former company First GBRf purchased 73208 and repainted it into BR Blue. In early 2009 73207 was repainted in Large Logo Blue and used for shunting duties in Whitemoor Yard. First GBRf also acquired 73141, 73212 and 73213, with all three painted in the new First Group livery; however, 73212 lacks the FirstGroup logo. 73141 was named 'Charlotte' in July 2009, which was known for being named twice in February 2009.[8] Now operated by the Eurotunnel Group, the trains are now being de-branded from the First Group branding. 73119 was purchased from Knights Rail Services in September 2011 and returned to service in June 2012. In 2013, Class 73s 73109 and 73136 were brought by GB Railfreight. They have since been repainted along with First GRBF liveried 73141, 212 and 73213 at St. Leonards Depot into GB Railfreight livery.

Merseyrail Electrics had a fleet of four Class 73/0 locomotives (numbers 73 001, 73 002, 73 004*, 73 005 & 73 006), based at Birkenhead North TMD, for use on shunting and other departmental duties. Two, numbers 73001 and 73006, were repainted into Merseyrail's yellow livery; they were later fitted with sandite discharging equipment and reclassified as Class 73/9.[10] All four locomotives were withdrawn from traffic by 2002, and all were later sold for preservation.

73 004 was used as a source of spare parts and was the first to be cut up.

Network Rail inherited two redundant Gatwick Express locomotives, numbers 73212 and 73213, from its predecessor Railtrack. These were overhauled and painted in the company's blue and green livery. They are used on engineering trains associated with an upgrade of electrical supply systems on the former Southern Region.

A third locomotive, number 73141, was originally bought for spare parts, but was returned to traffic in case of failure of one of the other two locomotives. The locomotives were later repainted into Network Rail all-over-yellow with red buffer beams.

In 2009, 73141 was acquired by First GBRf, with 73212 and 73213 following shortly afterwards.

South West Trains later expanded its fleet, by leasing two more locomotives from Porterbrook, numbers. 73201 and 73235. Both are former Gatwick Express locomotives. The first of these, number 73235, was overhauled in early 2005 and repainted in the new Desiro blue livery. It was joined by number 73201 later in the same year. Around the same time, number 73109 was also repainted into the new blue livery. 73109 was acquired by Transmart Trains in 2009.

The Class 73 Locomotive Preservation Company (C73LPC) formed in 2004 to manage locomotive 73136 at Stewarts Lane Depot, London.
73136, the last 73 operated by EWS was renamed "Perseverance", is now fully fitted with TPWS and OTMR equipment following the implementation of OTMR during the summer of 2006. The locomotive is registered for use on the national rail network and is available for either short term 'spot' hire or medium term contracts. The locomotive was hired to the Bluebell Railway during 2009 to assist with its Northern Extension to East Grinstead. In August 2006, the company was contracted by GBRf to repaint GBRf's 73208 into BR Blue for future use on charter work with 73136. The company has also restored 73210 at Stewarts Lane Depot, this locomotive is privately owned. The locomotive moved to its new home on the Mid Norfolk Railway in September 2008.

The Class 73 Locomotive Preservation Company changed ownership in 2009 and was renamed Transmart Trains in 2010. Following the takeover, the company expanded its operations and managed five Class 73 locomotives. These were 73109, 73118, 73133, 73136 and 73211. Number 73211 had been stripped for spares and is unlikely to return to service in its original form. 73133 has since been sold to a partner group of Transmart, and left Selhurst by road for a new life at Barry Island. Subsequently, the locomotive was transited by rail to South West Trains Bournemouth Depot on long term hire.

In 2013, Class 73s 73109 and 73136 were sold on for further use with GB Railfreight. They have since been repainted along with First GBRf liveried 73141, 73212 and 73213 at St. Leonards Depot into GB Railfreight livery.

No. 73951 (previously 73104 and E6010) at Eastleigh works on 31 October 2015 following conversion to Ultra73 specification.

Two locomotives, numbers 73211 and 73104, were completely rebuilt by Rail Vehicle Engineering Limited (RVEL)[11] of Derby. The 600 hp diesel engine was removed and replaced by a pair of Cummins QSK19 750 hp diesel engines, increasing the total diesel horsepower to 1,500.[12] The locomotives are used by Network Rail and are classified 73/9.[13] The Cummins QSK19 is the same engine used in the Class 220 and Class 221diesel multiple units. 73101 has been sold from preservation and will be added to the overhaul program. The first prototype of Network Rail's new ‘Ultra73′ locomotives was unveiled on Friday 13 June 2014 at RVEL in Derby.[14]

Commencing in 2013, five GB Railfreight Class 73s were re-engined as Class 73/9 by Brush Traction Wabtec at their factory in Loughborough. The first three converted locomotives, renumbered 73961-3 from 73209, 73204 and 73206 respectively, were fitted with MTU 1,600 hp V8 engines.[15] All existing mechanical and electrical components were removed prior to the re-fit, and the frontal appearance of the locomotives has been altered by the provision of light clusters and the installation of a more central location for the jumper cables. The dual driving positions have been retained although with a new design for the driver's controls. The refurbished locomotives will be capable of working with existing Class 73/1 and 73/2 units in either diesel or electric mode.[16]

The first completed locomotive, 73962 (ex-73204), was unveiled on 3 August 2014 at Brush Traction Loughborough. Another GBRf Class 73/9 locomotive, 73961 (ex 73209), has also been completed, and had undergone high-speed running tests on the Great Central Railway.

Several locomotives have been preserved on heritage railways, where perforce they run on their diesel engines: no preserved line has third rail electrification. They are particularly popular because they have a small diesel engine and hence are efficient with speeds normally limited to 25 mph, yet they are big mainline locomotives and thus more attractive than diesel shunters with similar-sized engines. Of note are the first built locomotive, No. 73001 (an ex-Merseyrail Class 73/9), and the former Pullman locomotive, No. 73101.

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Key:

In Service

Withdrawn / Stored

Preserved

Under Repair

Departmental

Scrapped

Numbers

Name(s)

Dates

Final Livery

Operator

Withdrawn

Status

Comments

Pre-TOPS

TOPS

E6001

73001

73901

-

-

-

BR Blue Large Logo

Merseyrail

05/2000

Preserved at Dean Forest Railway

E6002

73002

-

-

-

-

BR Blue Large Logo

Merseyrail

11/1995.

Preserved at Dean Forest Railway

Stored as surplus to requirements and used as spares at Kirkdale with 73005 (which was later resurrected). It is now preserved, although unlikely to run again. It is on static display at Lydney and used as a source of spares and storage. It is heavily stripped, although it retains power unit from 73132.

Out of service for most of 2010 awaiting new wheelsets and a repaint, this work was completed during early 2011 and was enhanced by an unexpected repaint into Intercity 'Executive' livery by St Leonards depot.

Stored early/mid-1996. Became source of spare parts for the Class 73 refurbishment programme at Stewarts Lane in July 1996 and to donate power unit to 73112 (now 73213) for reinstatement. Moved to Old Oak Common in early 1998 to provide further spares and officially withdrawn 1/1999. It was then moved to the Fire Service Training College at Moreton-in-Marsh and used for training exercising until sold for scrap 26/7/09.

E6034

73127

73203

-

-

-

Gatwick Express

First GBRf

05/2001

Withdrawn

Stripped for spares and scrapped, after periods in store at Peterborough, Tonbridge and St Leonards depots, during mid-2009.

Repainted from Gatwick Express livery at St Leonards Railway Engineering, released 09/12/13, moved back to Stewarts Lane 10/12/13.[ambiguous] Named Graham Stenning at Lovers Walk Depot 11 December 2015.

E6045

73138

-

-

-

-

Network Rail Yellow

Network Rail

-

In Service

E6046

73139

-

-

-

-

-

GB Railfreight

03/1999

Stored, Eastleigh Arlington.

E6047

73140

-

-

-

-

Network SouthEast

Spa Valley Railway

11/1998

Preserved at Tunbridge Wells West (75F).

First JB in preservation, private owned, on hire to the Spa Valley Railway in 2000. Repainted from BR Blue to Network SouthEast for Spa Valley Railway 2014 Diesel Gala.

E6048

73141

-

-

Ron Westwood / David GayCharlotte

2009-20092009-

GBRf Blue

GB Railfreight

-

In Service

Network Rail named 73141 twice (one name on each side) on 20 February 2009. By July 2009, the locomotive was in service with First GBRf.